1. Field of the Invention
The present invention relates generally to video signal recording/reproducing apparatuses having a built-in television standards converter, and more specifically, to a video signal recording/reproducing apparatus for standards conversion which requires aspect ratio conversion.
2. Description of the Related Art
In recent years, high definition television systems have been in the stage for practical application. The high definition television systems are not basically compatible with the existing television standards (such as NTSC and PAL). However, receivers, recording/reproducing apparatuses and the like dedicated to high definition television standards have hardly come into wide use, while for the existing television standards are widely spread such that almost everyone has at least one television set in his or her home. Therefore, a video signal recording/reproducing system has been advised by the present inventors, which includes therein television standards converter for converting a high definition television standard signal into an existing television standard signal. As an example, a converter will be described which converts a high definition television signal according to the MUSE (Multiple Sub-Nyquist Sampling Encoding) standard developed by NHK (Nippon Hoso Kyokai) into a television signal according to the existing NTSC standard. It is noted that a high definition television system generally has an aspect ratio greater than those for the existing television systems (referred to as wide aspect ratio). For example, the aspect ratio is 4:3 according to the NTSC standard, while the aspect ratio of a video image carried by a MUSE signal is 16:9.
Referring to FIG. 1, a conventional video signal recording/reproducing system includes a television standards converter 182 for converting a MUSE signal 188 into a picture image of an NTSC signal, and a recording/reproducing apparatus 184 of NTSC standard for recording the NTSC signal output from television standards converter 182 on a magnetic tape 200 utilizing a rotary head mounted to a rotary drum 198 and reproducing the recorded signal. A reproduced NTSC signal 194 output from recording/reproducing apparatus 184 can be displayed as it is at a television receiver 186.
Television standards converter 182 includes a MUSE/NTSC signal processing circuit 190 for performing a de-emphasis processing to an input MUSE signal, a time-base conversion processing from the MUSE signal to an NTSC signal, and a thinning processing of scan lines, thereby converting the MUSE signal into an NTSC signal, and a vertical filter 192 for performing a prescribed processing to the NTSC signal output from MUSE/NTSC signal processing circuit 190, eliminating the deformation of the image of the NTSC signal output from circuit 190, and producing a video signal permitting of displaying the resultant image in a normal form on a picture frame of NTSC standard. Vertical filter 192 is provided with an aspect ratio selection switch 196 for selecting either matching the aspect ratio of the image to the image of the original MUSE signal or to that of the image of the NTSC signal, when the deformation of the image is removed away.
The apparatus shown in FIG. 1 operates as follows. Referring to FIG. 2, the MUSE signal 188 input to MUSE/NTSC signal processing circuit 190 produces a picture frame A at an aspect ratio of 16:9. As described above, MUSE/NTSC signal processing circuit 190 performs the de-emphasis processing to the MUSE signal, the time-base conversion processing, the thinning of scan lines and the like, thereby compressing the picture frame horizontally as illustrated in FIG. 2, and a video signal having an aspect ratio of 4:3 is output as a result. Such a picture frame horizontally compressed and having the aspect ratio of 4:3 will be referred to as compressed entire picture frame display. The image signal of the compressed entire picture frame display B has been converted to an NTSC signal and when applied and displayed at a television system as it is, as illustrated in FIG. 2, what has been a true circle in the original picture frame A is deformed into a longwise ellipse. The deformation must therefore be eliminated.
The vertical filter 192 is provided for eliminating the deformation. There are two ways of elimination. The first way is to eliminate the deformation by cutting away both sides of the compressed entire picture frame display B and expanding the central portion of the image in the horizontal direction. The second way is to eliminate the deformation by compressing the picture frame in the vertical direction without cutting the both sides, as illustrated in a picture D in FIG. 2. In the latter, a thinning processing of scan lines or the like is performed.
The signals processed as the picture frames C and D are recorded on magnetic tape 200 at recording/reproducing apparatus 184 in FIG. 1.
Reproduction is performed in the same manner as usual reproduction of an NTSC signal. More specifically, recording/reproducing apparatus 184 reproduces the NTSC signal recorded on magnetic tape 200. The reproduced NTSC signal 194 is applied to television receiver 186 and the picture frame C or the picture frame D shown in FIG. 2 is displayed as a result.
Among conventional systems, if the side-cut display C (see FIG. 2) is recorded on a magnetic tape, data on cut-away portions on both sides of the image drops out. The entire original image cannot be reproduced at the time of reproduction. In high definition television programs, some information is usually displayed at the right and left edges of a picture frame, naturally taking into account the wide aspect ratio. It is not desirable that the information on both sides drops out as such and cannot be reproduced.
In contrast, in a system utilizing the entire picture frame display D, the problem described above is not encountered. However, portions with no video image in the upper and lower parts of a picture frame are included in a signal to be recorded. In view of efficiency, recording portions with no image as this is to waste a part of the recording medium. It is more preferable to eliminate such a waste.